proemptosis

from The Collaborative International Dictionary of English v.0.48

Proemptosis \Pro`emp*to"sis\, n. [NL., from Gr. ? to fall in
   before; ? before + ? in + ? to fall.] (Chron.)
   The addition of a day to the lunar calendar. [R.] See
   {Metemptosis}.
   [1913 Webster]